code: def get_smiles(self, idx):
      return self.vocab[idx]
  
file_path: dgl/examples/pytorch/jtnn/jtnn/mol_tree.py
imports: import copy
  import rdkit.Chem
label_desc: Use image node_id 3 for calling the Vocab obj's underlying member method code with example usage: obj.get_smiles(idx) and returns: self